Synthesis and characterization of poly (1,6‐hexamethylene oxamide‐co‐m‐xylene oxamide) copolymers

Abstract

To modify the properties of poly (hexamethylene oxamide) (PA62), m-xylylene diamine (MXD) was introduced into the polyamide main chain. A series of high molecular weight PA62/MXD2 were synthesized via a two-step method. The chemical structure of polymer was analyzed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy, and the results confirmed the formation of PA62/MXD2. DSC test showed that the T m of the copolymers were decreased as the molar contents of MXD in the range of 10 to 50 mol %. TGA analysis revealed that the thermal stability of the copolymers compared well with commercial PA6. Wide-angle X-ray diffraction studies suggested the copolymers with MXD content of 0 to 10 mol % possessed high crystallinity. The water uptake measurements were monitored, and the saturated water absorptions were found to be lower than 2.5 wt %. These properties gave them a competitive edge for application where precise dimensional stability and high thermal resistanceproperties are required.

Synthesis and characterization of poly(hexamethylene terephthalate/hexamethylene oxamide) alternating copolyamide (alt‐PA6T/62)

“…According to Figure 5 ( a ) , ran‐PA6T/62 displayed an obvious glass transition temperature ( T g ) and a broad melting peak, which indicated that with the incorporation of 6 T units, the crystallization of 62 units was strongly restrained and resulted in low crystallinity. Compared with ran‐PA6T/62 ( T m = 294°C, ΔH f = 17 J g −1 , T c = 243°C, ΔH c = 18 J g −1 ), which possesses decreased crystallinity, 27–29 the molecular chain arrangement of alt‐PA6T/62 is more regular, and the corresponding crystal properties and thermal properties are improved. These results demonstrate that PA6T/62 alternating copolyamide displayed both high temperature resistance and excellent processing properties.…”

“…In this method, polyoxamides with η int = 1.9 were prepared. Recently, much research on polyoxamides has been reported by utilizing this two‐step polymerization method, and high‐performance polyoxamides have been successfully synthesized 24–29 …”

“…However, the disordered inclusion of various structures in the random copolyamides destroys the sequence structure regularity of the molecular chain and hinders the formation of hydrogen bonds between the chains. Therefore, random copolyamides often exhibit reduced crystallinity, resulting in relatively low T m , high water absorption, and poor dimensional stability 28,29 . Compared with that of random copolyamides, the molecular chain arrangement of alternating copolyamides is more regular, and the corresponding crystal properties and thermal properties are improved.…”

“…Recently, much research on polyoxamides has been reported by utilizing this two-step polymerization method, and high-performance polyoxamides have been successfully synthesized. [24][25][26][27][28][29] Comonomers are commonly utilized in polyamides to change the melt temperature and improve the processability. In this way, random copolyamides can be easily prepared.…”

“…Therefore, random copolyamides often exhibit reduced crystallinity, resulting in relatively low T m , high water absorption, and poor dimensional stability. 28,29 Compared with that of random copolyamides, the molecular chain arrangement of alternating copolyamides is more regular, and the corresponding crystal properties and thermal properties are improved. DSM 30 recently disclosed a patent for preparing copolyamides possessing alternating repeating units, which have a strictly alternating structure and exhibit high-temperature resistance compared with random copolyamides with the same composition.…”